Day 1 M5: connecting to the internet Flashcards
silos of devices that connect to the internet:
desktop, laptops, servers, data centers, routers, switches, tablets, cell phones, ATM, industrial equipment, medical devices, cars.
Physical layer
cabling
data link layer
ethernet
What is PSTN, or POTS?
The existing infrastructure of the public telephone network. Public Switched Telephone network, or PSTN. Plain Old Telephone Service.
a system built using the POTS, or PSTN, the phone line to transmit data. A permanent precursor to dial-up networks. A form of this is still in use today.
Usenet
uses POTS for data transfer. Gets its name because the connection is established by dialing a phone number. awful sound. May be the only option in some rural communities, even today. It used to be the main way computers communicated over long distances. We’d have to choose between using the phone or using the internet.
Dial-up connection
How is transferring data across a dial up connection done?
through modems.
modulator demodulator. They take data computers can understand and turn them into audible wavelengths that can be transmitted over POTS, similar to how line coding turns ones and zeroes into modulating electrical charges across ethernet cables.
What is a modem?
baud rates of early modems
very low.
A measurement of how many bits could be passed across a phone line in a second
baud rate
Baud rate in 1950s
110 bits per second.
Usenet development baud rate
300 bits per second
baud rate by 1990s, when internet became commodity
14.4 kilo bits per second.
Another term for POTS, or Plain old telephone service
Public switched telephone network
a baud rate is a measurement of the number of
bits that can be sent across a telephone line every second.
What system did Duke grads build that is still in use today?
Usenet
what device is used to transfer data across a dial-up connection?
Modem
Modems take data that computers can understand and turn them into ____ that can be transmitted over POTS
audible wavelengths
any connectivity technology that isn’t dial-up internet. Almost always faster than even the fastest dial-up. Refers to connections that are always on. There are long-lasting connections that don’t need to be
Broadband defined in terms of internet connectivity
what is faster, dial up or broadband
broadband
Does broadband or dial-up have long-lasting connections that don’t need to be established with each use, and are always present? connections that are always on?
broadband
What were T-carrier technologies invented to do?
transmit multiple phone calls over a single link.
What was common in businesses by the 90’s?
Using T-carrier technologies.
T-carrier technologies became
common transmission systems to transfer data faster than dial-up.
image loading on dial-up
took many seconds to download and display
a 2mb high res photo download speed on fastest dial up
20 minutes, with a baud rate of 14.4 kb per second, to download 16,777,216 bits.
what wouldn’t we have so much transmission of without broadband?
Pictures and videos.
What do T-carrier technologies require, which makes them expensive?
dedicated lines. You usually only see them in use by businesses.
